1. Field of the Invention
The present invention relates to a power steering device for steering a boat propulsion unit with a hydraulic cylinder unit which is connected in ganged relationship to a steering wheel.
2. Description of the Prior Art
One conventional power steering device for steering a boat propulsion unit is disclosed in Japanese laid-open patent publication No. 2-147497, which corresponds to U.S. Pat. No. 4,976,639. The disclosed power steering device has a cable assembly coupled to and extending from a steering wheel, the cable assembly comprising a sheath and a core inserted therein. The core is fixed to a bracket on a distal end of the piston rod of a hydraulic cylinder unit which angularly moves the boat propulsion unit in a horizontal direction. The sheath is attached to a steering tube which can be moved in response to operation of the steering wheel. When the steering tube is moved by the steering wheel, the movement of the steering tube is transmitted through a gear or a lever to a spool valve, which delivers working oil from a pump to a left (upper) chamber or a right (lower) chamber of the hydraulic cylinder unit, thus moving the piston rod. When the piston rod is thus moved, a steering arm coupled thereto is angularly moved thereby steering the boat propulsion unit.
In the disclosed power steering device, the steering tube, the spool valve, and the rod of the hydraulic cylinder unit have respective axes lying parallel to each other in order to achieve a simple assembly for transmitting the movement of the cable assembly to the hydraulic cylinder unit. Therefore, the steering tube, the spool valve, and the hydraulic cylinder unit are required to be installed highly accurately in place relative each other. Because of the high assembling accuracy required, the conventional power steering device is manufactured relatively expensively in a relatively complex process.